Developer apparatus for heat developing paper

ABSTRACT

An image developer for heat developing paper, such as dry silver paper, wherein a curved platen is heated by passing a current therethrough, thereby obtaining very quick heating time and very uniform heat. A belt means, such as a fabric belt, is held by rollers snugly against the platen surface that is heated, and the belt is driven by connecting the rollers to a motor and the paper to be developed is inserted between the fabric belt and the platen and caused to move about the heated platen, thereby providing &#39;&#39;&#39;&#39;averaging&#39;&#39;&#39;&#39; the heat to the paper.

United States Patent [72] Inventors PaulJ.Crane Torrance; Glenn A.Reese, San Pedro, both of Calif. [21] Appl. No. 819,066 (22] Filed Apr.24, 1969 [45] Patented Nov. 16, 1971 [73] Assignee The Magnavox CompanyFort Wayne, Ind.

[54] DEVELOPER APPARATUS FOR HEAT DEVELOPING PAPER 7 Claims, 6 DrawingFigs.

[52] U.S. C1 219/388, 34/151, 34/164, 219/243, 219/541, 219/469, 219/494[51 Int. Cl F271) 9/06 [50] Field of Search 219/216,

[ 5 6] References Cited UNITED STATES PATENTS 2,569,773 10/1951 Orr219/543 2,977,450 3/1961 Boicey 219/541 3,302,002 1/1967 Warren 219/5433,506,804 4/1970 Schippers et al. 219/388 2,532,562 12/1950 Lorig219/469 2,629,808 2/1952 Ulmschneider. 219/243 2,557,983 6/1951 Linder219/543 2,939,223 6/1960 Smith 34/58 3,113,198 12/1963 Shinn 219/243 X3,294,947 12/1966 Whitmore 219/469 X 3,449,547 6/1969 Goodman et al.219/216 Primary Examiner- Volodymyr Y. Mayewsky A!!0rnt \X-Jffl8 andYoung and Richard T. Seeger ABSTRACT: An image developer for heatdeveloping paper, such as dry silver paper, wherein a curved platen isheated by passing a current therethrough, thereby obtaining very quickheating time and very uniform heat. A belt means, such as a fabric belt,is held by rollers snugly against the platen surface that is heated, andthe belt is driven by connecting the rollers to a motor and the paper tobe developed is inserted between the fabric belt and the platen andcaused to move about the heated platen, thereby providing averaging" theheat to the paper.

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SHEET 3 [1F 3 PAPER 961 lNSERTlON INVENTORS GLENN A. QEESE AUL J. CRANEHQWHAQDT. SEEGER Aflorney DEVELOPER APPARATUS FOR HEAT DEVELOPING IPAPER One of the major problems in previous devices for developingpreviously exposed heat-sensitive paper, such as dry silver paper, wasthe inability to provide a unit which would quickly heat to thenecessary temperature and which would provide uniform heat to the entiresurface of the paper. Quick heating is necessary since many developingmachines are not continually used and therefore it is impractical tokeep the developer turned on continuously since this not only wastespower but tended to burn out the heating elements in the developer.However, in previous devices it took relatively long periods of time toraise the developing device to the proper temperature and a furtherperiod of time to insure that the developer surface was of uniformtemperature. Uniform temperature is needed since otherwise the paperwhich is developed will have streaks and spots corresponding to thenonuniform heating of the developer.

Previous devices relied primarily on a plurality of small resistivedevices insulated from one another and also insulated from a metallicsurface for heating the paper in the developer. In order to heat thesurface in the developer, it was necessary for the heat from theresistive elements to be transferred to the surface and an additionalperiod of time was necessary until the heat alongthe surface of thedeveloper had sufficient time to flow across the surface of thedeveloper had sufficient time to flow across the surface to obtain auniform temperature.

This invention overcomes these deficiencies by providing a platenthat isheated directly by the power source. This not only reduces significantlythe time that it takes for the platen to reach the temperature neededfor developing but since the platen itself is being heated, by havingthe current flow therethrough, the temperature in the platen surface isat all times uniform, thereby making unnecessary a long waiting time toobtain unifonnity of temperature.

It is therefore an object of this invention to improve and advance theart in image developers using heat-sensitive paper, such as dry silverpaper, to widely increase the use of such developing techniques.

Another object of this invention is to provide a heating platen in adeveloper of the kind referred to above that has current passingdirectly therethrough for reduced heating time and uniformity of surfaceheat.

It is a further object of this invention to cause the paper to moverelative to the surface of the heated platen and to keep the paper inclose contact therewith to further improve upon the uniformity of theheating of the paper.

Another object of this invention is to provide means for maintaining thepaper in close contact with the platen by having a belt driven over theplaten and by inserting the paper between the belt and the platen. Meansare provided to cause the belt to be agitated or moved relative to thepaper as it carries the paper over the platen so that any high spots onthe belt will be averaged over an area of the paper, thereby furtherimproving uniformity of heating of the paper.

Another object of this invention is to provide a polished platen tofacilitate uniform movement of the paper over the platen, improve heattransfer from the platen to the paper, and to improve uniformity ofheating of the paper.

These and other objects of this invention will become more apparent whena specific embodiment is considered in connection with the followingdrawings:

FIG. 1 is a perspective, schematic view of a preferred embodiment ofthis invention;

FIG. 1A is a sectional view of an embodiment of this invention where theplaten'has notched ends to control the temperature of the platen at theends thereof;

FIG. 2 is a perspective, schematic view of the paper drive of FIG. -Iand is shown separately for clarity;

FIG. 3 paper heating mechanism, is a schematic circuit diagram of meansfor maintaining the surface of the platen at a predeterminedtemperature;

FIG. 4 is a plan view of the belt paper drive wherein the belt driverollers are mounted eccentrically; and

FIG. 5 Is a section taken at $--5 of the paper drive of FIG. 4.

In FIG. 1 is shown a resistive element heating platen 20 which may beten-thousandths of an inch thick and may be of a light gauge inconel ornichrome. Plate'n 20 is a truncated drum and has attached at each end aconductive end plate 22 which may be of copper or other highlyconductive material. For certain applications platen 20 may be coatedwith a plastic such as "Teflon" or other similar material.

Attached to copper end plates is a metallic strap 24 which also may beof copper and which passes through the central opening of transformercore 26. The primary winding 28 of transformer core 26 has a very largenumber of turns compared with the secondary winding which is shown as asingle turn but may be more than one tum and comprises strap 24, endplate 22, and platen 20. The primary is connected to temperatureservocontrol 28 which will be later described.

The ends of platen 20 may have notches 30 as shown in FIG. 3. Thepurpose of placing notches 30 at the ends of platen 20 is to increasethe current flow in the legs 32 of the notches, thereby raising thetemperature of these legs in comparison with the surface of platen 20 tocompensate for the normal cooling that the edges would have.

PAPER DRIVE MECHANISM The paper drive mechanism is shown in FIG. 2 whereplaten 20 has been removed from its power source for clarity. In thisembodiment the platen 20 is stationary while rollers 34, 36 are placedbelow the platen and rollers 38, 40 are placed above the platen with anendless cloth belt 42 wrapped tightly about the platen surface and thenaround the outside of the rollers 34, 36, 38, and 40, which are mountedfor rotation about their axes. (The supports for the axes are notshown.) Rollers 34 and 36 are driven by belt 44 which in turn is drivenby motor 46.

Attached to lower edges of platen 20 are guides 48, 49. If drive motor46 is in the on" condition, the placement of paper 50 on guide 48between belt 42 and platen 20 will cause the paper to become engagedbetween the belt 42 and the platen 20 to carry the paper around theplaten 20 as the belt is driven by motor 46. The paper 50 may be placedwith emulsion side against platen 20 or, if the emulsion tends to stickto platen 20, it may be placed with emulsion side away from platen 20.This insures unifonnity of heating of the dry silver paper since ifthere are any unevenly heated areas of platen 20 due to defects in theplaten surface, there will be a tendency to average" these nonuniformareas with the other areas of platen 20.

When power is supplied to primary 28, a large current is developedthrough strap 24, end plates 22, and platen 20. This will bring thetemperature of platen 20 quickly and uniformly to developingtemperature, thereby providing an improved device. Servo TemperatureControl CircuitA temperature control circuit such as shown in FIG. 3 maybe used to maintain the temperature of platen 20 at a constant level.The specific structure shown is known to the art but will be brieflydescribed thereof. A temperature sensor 52 of the thermistor type isplaced on the underside of platen 20 and is in contact therewith tosense the temperature, and thermistor S2 is connected as indicated incircuit of FIG. 3. Line voltage 54 is applied to a full wave rectifier56 through a transformer 58 to supply a voltage to voltage dividercircuit which supplies a pulse to transformer 60 with the pulses havinga frequency similar to that of the line voltage frequency but having aperiod, or time per pulse that the energy is applied inversely,proportional to the temperature of thermistor 52; the cooler thethermistor 52, the longer the period, and the warmer the thermistor, theshorter the period. The purpose of this type of circuit is to provide acircuit that is extremely responsive to the thermistor temperature.

The manner in which the thermistor controls the pulse periods will nowbe described. Thermistor 52 controls the outut of transistor 62 which inturn charges a capacitor 64 and when capacitor 64 voltage reaches apredetermined level, a unijunction transistor 66 turns on immediately.Unijunction transistors are very responsive to voltage level and reactalmost instantaneously to a given voltage level.

Transistor 66 stays on until the instantaneous line voltage goes throughzero, at which time it turns off. The pulse applied by transistor 66 ispassed through the primary 68 of transformer 60 and the secondaries 70and 72 of transformer 60 are connected through SCR devices 74 and 76respectively to the primary 28 of the heater circuit shown in FIG. 1.The SCRs 74 and 76 are connected so that one of them will fireregardless of the polarity of line voltage 54. A neon light 78 isconnected across primary 28 and glows according to the current beingapplied to primary 28 so that at any time it is possible to tellvisually whether the platen 20 is being charged and to what extent. ifthe thermistor S2 is relatively cool, then the on time of transistor 62will be larger whereas if the thermistor S2 is relatively warm and abovethe predetermined temperature then the on time of transistor 62 will beshorter, thereby keeping the power applied to the primary 28 and platen20 at the proper level to maintain a given temperature.

FIG. 4 shows only the paper drive for the embodiment shown in thisinvention.

Belt 80 is driven by rollers 82, 84 which in turn are driven by motor 86through a primary drive belt 88 which is driven by pinion 90 and gear 92which are concentrically mounted. A secondary timing belt 94 havinginternal gearing projections 96 thereon is wound around gears 93, Iwhich are attached respectively to rollers 82, 84. Heated platen 22 isplaced between rollers 82 and 84 and below idler roller W2 and belt 80is wound around rollers 82, 84, 102 and passes over the upper surface ofplaten 22. The paper to be heated is inserted between the belt 80 andplaten 22.

The rollers 82, 84 are supported for rotation on eccentric shafts 104,106 respectively so that as they are driven for rotation by drive belt94, they are caused to wobble and assume position 82A and 84A shown bydotted lines, during the rotation. This causes the belt 80 to rubagainst and move relative to the paper as the paper is being movedacross platen 22 and thereby averages out the contact of any high spotson the belt with the paper. Without this rubbing or agitation of thebelt over the paper as it is driving the paper, high spots may cause thepaper to become unevenly heated and hence to have the pattern of thebelt printed" on the paper. With the agitation of the belt 80, thisunevenness is overcome.

While the invention has been disclosed and described in some detail inthe drawings and foregoing description, they are to be considered asillustrative and not restrictive in character, as modifications mayreadily suggest themselves to persons skilled in this art and within thebroad scope of the invention, reference being had to the appendedclaims.

What is claimed is:

1. Apparatus for quickly and uniformly heating an exposed heatdeveloping type paper comprising:

a curved platen comprised of a single layer of resistive material,adapted to engage on the convex side thereof the heat developing paper,

moving means held snugly against the convex surface of said platenlayer, and movable relative to said layer,

means for driving said moving means relative to said layer,

guide means for receiving the paper and guiding the paper between saidmoving means and said platen layer to cause the paper to move over saidplaten layer as said moving means is driven over said platen layer,

electrical power means connected to said platen layer for causingcurrent to flow through said layer of resistive material andcorrespondingly heat said layer,

means to sense the temperature of said platen layer and correspondinglycontrol the power of said platen layer to maintain said platen layer ata predetermined temperature, means for causing said moving means to beagitated relative said paper, as said moving means is moving said paperover said platen layer thereby minimizing the moving means surfaceconfiguration from being imprinted on said paper.

2. Apparatus of claim 1 with said electrical power means comprising atransformer having a primary winding of many turns and having asecondary winding of less than six turns,

said platen layer being in said secondary winding of less than sixturns.

3. The apparatus of claim 1 with said electrical power source comprisinga transformer core,

a primary winding of many turns being on said transformer core and beingconnected to said power source,

said platen means being in the secondary winding of said transformercore and having substantially fewer windings than said primary winding.

4. Apparatus of claim 1 with said platen means having notches cut alongits periphery to form a plurality of spaced legs along the periphery andto concentrate current flow in the legs thereby raising the temperaturein the legs to insure more uniform temperature of the platen means.

5. The apparatus of claim 1 with said means for moving the heatresponsive member comprising belt means which is driven over said platensurface,

roller means around which said belt means is placed being positioned tohold said belt means in intimate contact with said platen surface,

said roller means being mounted for eccentric rotation to cause saidbelt means to have a reciprocal movement relative said heat-responsivemember as said belt means is moving over said platen surface.

6. Apparatus in claim 1 with means for moving the paper over said platensurface as the paper is being developed to provide an average heat tosaid paper to insure uniform heating of said paper,

said platen surface being polished to facilitate movement of the paperover the surface, improve heat transfer to the paper from the surfaceand improve heating uniformity of the paper.

7. Apparatus for quickly and uniformly heating an exposed heatdeveloping type paper comprising:

a curved platen comprised of a single layer of resistive materialadapted to engage on a convex side thereof the heat developing paper,

moving means held snugly against the convex surface of said platenlayer, and movable relative to said layer,

means for driving for said moving means relative to said layer,

guide means for receiving the paper and guiding the paper between saidmoving means and said platen layer to cause the paper to move over saidplaten layer as said moving means is driven over said platen layer,

electrical power means connected to said platen layer for causingcurrent to flow through said layer of resistive material andcorrespondingly heat said layer,

means to sense the temperature of said platen layer and correspondinglycontrol the power to said platen layer to maintain said platen layer ata predetermined temperature,

a plurality of spaced legs being along a periphery of said platen meanswith said legs being between said electrical power means and said platenlayer so that the current flowing through said platen layer flowsthrough said legs causing a higher current density in said legs therebyraising the temperature in the legs to assure more uniform temperaturein the remainder of the platen layer.

i t it 0' k

1. Apparatus for quickly and uniformly heating an exposed heatdeveloping type paper comprising: a curved platen comprised of a singlelayer of resistive material, adapted to engage on the convex sidethereof the heat developing paper, moving means held snugly against theconvex surface of said platen layer, and movable relative to said layer,means for driving said moving means relative to said layer, guide meansfor receiving the paper and guiding the paper between said moving meansand said platen layer to cause the paper to move over said platen layeras said moving means is driven over said platen layer, electrical powermeans connected to said platen layer for causing current to flow throughsaid layer of resistive material and correspondingly heat said layer,means to sense the temperature of said platen layer and correspondinglycontrol the power of said platen layer to maintain said platen layer ata predetermined temperature, means for causing said moving means to beagitated relative said paper, as said moving means is moving said paperover said platen layer thereby minimizing the moving means surfaceconfiguration from being imprinted on said paper.
 2. Apparatus of claim1 with said electrical power means comprising a transformer having aprimary winding of many turns and having a secondary winding of lessthan six turns, said platen layer being in said secondary winding ofless than six turns.
 3. The apparatus of claim 1 with said electricalpower source comprising a transformer core, a primary winding of manyturns being on said transformer core and being connected to said powersource, said platen means being in the secondary winding of saidtransformer core and having substantially fewer windings than saidprimary winding.
 4. Apparatus of claim 1 with said platen means havingnotches cut along its periphery to form a plurality of spaced legs alongthe periphery and to concentrate current flow in the legs therebyraising the temperature in the legs to insure more uniform temperatureof the platen means.
 5. The apparatus of claim 1 with said means formoving the heat responsive member comprising belt means which is drivenover said platen surface, roller means around which said belt means isplaced being positioned to hold said belt means in intimate contact withsaid platen surface, said roller means being mounted for eccentricrotation to cause said belt means to have a reciprocal movement relativesaid heat-responsive member as said belt means is moving over saidplaten surface.
 6. Apparatus in claim 1 with means for moving the paperover said platen surface as the paper is being developed to provide anaverage heat to said paper to insure uniform heating of said paper, saidplaten surface being polished to facilitate movement of the paper overthe surface, improve heat transfer to the paper from the surface andimprove heating uniformity of the paper.
 7. Apparatus for quickly anduniformly heating an exposed heat developing type paper comprising: acurved platen comprised of a single layer oF resistive material adaptedto engage on a convex side thereof the heat developing paper, movingmeans held snugly against the convex surface of said platen layer, andmovable relative to said layer, means for driving for said moving meansrelative to said layer, guide means for receiving the paper and guidingthe paper between said moving means and said platen layer to cause thepaper to move over said platen layer as said moving means is driven oversaid platen layer, electrical power means connected to said platen layerfor causing current to flow through said layer of resistive material andcorrespondingly heat said layer, means to sense the temperature of saidplaten layer and correspondingly control the power to said platen layerto maintain said platen layer at a predetermined temperature, aplurality of spaced legs being along a periphery of said platen meanswith said legs being between said electrical power means and said platenlayer so that the current flowing through said platen layer flowsthrough said legs causing a higher current density in said legs therebyraising the temperature in the legs to assure more uniform temperaturein the remainder of the platen layer.